From:             7willows at dsl dot pipex dot com
Operating system: SunOS ts10 5.11 snv_115 i86pc 
PHP version:      5.2.10
PHP Bug Type:     Math related
Bug description:  multiplication by zero problem

Description:
------------
I have a function which is used to assign values into a number of global
arrays. Two of the arrays are assigned values that are generated using the
rand() function. A third array holds the result of the multiplication. When
both first two arrays are assigned a value of 0 (zero), the result of the
multiplication is 1 and not 0.

This information is then entered into a html form and presented to the
user and they are asked to enter the results of 

$numfacttest[$a] / $randval[$a] = useranswer

The useranswer is then compared to $answer[$a] which is already
calculated. The problem is that 0 * 0 is returning the answer 1 sometimes.

Reproduce code:
---------------
function setnumberfacttest($count,$maxnumberfacts) {
   global $numfacttest, $answer, $operator, $randval;
   for ($a=0 ; $a < $count ; $a++) {
       $operator[a]=chr(247);
       $bit1=rand(0,$maxnumberfacts);
       $bit2=rand(0,$maxnumberfacts);
       $numfacttest[$a]=$bit1 * $bit2;
       $randval[$a]=$bit2;
       $answer[$a]=$bit1;
   }

}

Expected result:
----------------
Actual Results with hidden value displayed

2 / 1 = <useranswer> 2
0 / 0 = <useranswer> 0
0 / 0 = <useranswer> 0
2 / 2 = <useranswer> 1
4 / 2 = <useranswer> 2
1 / 1 = <useranswer> 1
0 / 0 = <useranswer> 0
0 / 0 = <useranswer> 0
0 / 0 = <useranswer> 0
1 / 1 = <useranswer> 1


Actual result:
--------------
Actual Results with calculated hidden value displayed

2 / 1 = <useranswer> 2
0 / 0 = <useranswer> 1
0 / 0 = <useranswer> 0
2 / 2 = <useranswer> 1
4 / 2 = <useranswer> 2
1 / 1 = <useranswer> 1
0 / 0 = <useranswer> 1
0 / 0 = <useranswer> 0
0 / 0 = <useranswer> 2
1 / 1 = <useranswer> 1


-- 
Edit bug report at http://bugs.php.net/?id=48904&edit=1
-- 
Try a CVS snapshot (PHP 5.2):        
http://bugs.php.net/fix.php?id=48904&r=trysnapshot52
Try a CVS snapshot (PHP 5.3):        
http://bugs.php.net/fix.php?id=48904&r=trysnapshot53
Try a CVS snapshot (PHP 6.0):        
http://bugs.php.net/fix.php?id=48904&r=trysnapshot60
Fixed in CVS:                        
http://bugs.php.net/fix.php?id=48904&r=fixedcvs
Fixed in CVS and need be documented: 
http://bugs.php.net/fix.php?id=48904&r=needdocs
Fixed in release:                    
http://bugs.php.net/fix.php?id=48904&r=alreadyfixed
Need backtrace:                      
http://bugs.php.net/fix.php?id=48904&r=needtrace
Need Reproduce Script:               
http://bugs.php.net/fix.php?id=48904&r=needscript
Try newer version:                   
http://bugs.php.net/fix.php?id=48904&r=oldversion
Not developer issue:                 
http://bugs.php.net/fix.php?id=48904&r=support
Expected behavior:                   
http://bugs.php.net/fix.php?id=48904&r=notwrong
Not enough info:                     
http://bugs.php.net/fix.php?id=48904&r=notenoughinfo
Submitted twice:                     
http://bugs.php.net/fix.php?id=48904&r=submittedtwice
register_globals:                    
http://bugs.php.net/fix.php?id=48904&r=globals
PHP 4 support discontinued:          http://bugs.php.net/fix.php?id=48904&r=php4
Daylight Savings:                    http://bugs.php.net/fix.php?id=48904&r=dst
IIS Stability:                       
http://bugs.php.net/fix.php?id=48904&r=isapi
Install GNU Sed:                     
http://bugs.php.net/fix.php?id=48904&r=gnused
Floating point limitations:          
http://bugs.php.net/fix.php?id=48904&r=float
No Zend Extensions:                  
http://bugs.php.net/fix.php?id=48904&r=nozend
MySQL Configuration Error:           
http://bugs.php.net/fix.php?id=48904&r=mysqlcfg

Reply via email to